


It's Because of You

by M34GS



Series: Haikyuu! Merperson AU [3]
Category: Haikyuu!!
Genre: AU, Abandonment, Abuse, Adoption, Aged Down Characters, Aged up characters, Anxiety, Apologies, Family, Family Issues, Forgiveness, M/M, Orphans, Post-Traumatic Stress Disorder - PTSD, Reforming, domestic abuse/violence, merperson au
Language: English
Status: In-Progress
Published: 2020-08-08
Updated: 2020-08-30
Packaged: 2021-03-06 07:21:53
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 7,255
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25779634
Author URL: https://archiveofourown.org/users/M34GS/pseuds/M34GS
Summary: Yuutarou was the second child adopted by Hajime and Tooru. He has always wanted to prove himself as a good child and find his place in the Pod. However, when a new addition is brought into the family, quite abruptly, he feels displaced.Can he learn to understand this new member of his family, and even grow to love him as a brother, or does his jealousy run too deep?
Relationships: Akaashi Keiji/Bokuto Koutarou, Hanamaki Takahiro/Matsukawa Issei, Hinata Shouyou/Kageyama Tobio, Iwaizumi Hajime/Oikawa Tooru, Kozume Kenma/Kuroo Tetsurou
Series: Haikyuu! Merperson AU [3]
Series URL: https://archiveofourown.org/series/1781167
Comments: 16
Kudos: 24





	1. The Stranger

**Author's Note:**

> Hey! So, this is the start of the future of the merperson AU I started for Haikyuu!!  
> I'm super excited. I know it's been a while, but I needed a bit of a break from writing about merpeople. So I did some other stuff and now I'm back! None of the ages are what they were in canon, as the merpeople age differently than humans. This fanfic takes place after 'Lost'. There will be more of a focus on the Iwaizumi-Oikawa family in this one, but there will be more to come to explore dynamics between the families of other pairings. Enjoy!

Tooru hummed to himself as he watched his children. Issei twisted and turned in the water easily, with a lazy grin. His messy dark hair framed his face and his thick eyebrows were raised in amusement. His teal-coloured tail shimmered in the water, long and graceful. Chasing after him was his younger adopted brother, Yuutarou. Yuutarou’s hair was short and, unlike his brother’s, stood straight up in spikes. He was shorter and not quite as graceful. But he tried hard. There were very few forces in the ocean that Tooru would consider greater than Yuutarou’s stubbornness.

Right now, that stubbornness had him chasing his older brother around in circles. Tooru shook his head and smiled. Issei would let his younger brother get closer…closer…closer…and then dart away at the last minute. Granted, he was quite a few decades older than Yuutarou, and Yuutarou was not the most graceful swimmer in the pod.

The water around them refracted the light of the sun, throwing beautiful patterns along the ocean floor. Tooru never did understand how someone would prefer life above the water. Everything was so much prettier down here. The seaweed swayed in the gentle tug of the ocean, and fish of every colour darted back and forth. His sons’ voices rang through the water; Issei full of laughter while Yuutarou shouted at him in frustration.

Tooru smiled and settled on the sand. He allowed himself to relax and his eyes slid closed, a gentle smile on his face. His sons were happy, and in a little while they would go back to their den and meet up with Hajime. He was patrolling their territory today, and Tooru couldn’t wait to see him that night. He refrained from using his affinity to contact him telepathically…it wouldn’t be fair to distract him from his duties.

A strangled cry of distress broke through Tooru’s thoughts and had him bolting upright. He scanned the area, eyes catching sight of his sons almost immediately. They were still playing. Relief surged through him and he relaxed slightly, until he heard the cry again, more desperate this time. This time, he noticed his sons stopped in their playing, confusion flashing across their faces. A scar on Tooru’s tail started to ache, his body responding to a distant memory…one of ships and harpoons and humans. He swallowed and glanced around frantically. He could see no humans here, but that didn’t mean there weren’t any.

An image flashed through his mind: a net of mer, tails flashing different colours in distress, the way only one pod could, and the youngest, struggling to breathe above the water. Tooru shook his head, willing the image out of his mind. He swam over to his two sons.

“Issei. Yuutarou,” he called. His children stopped looking around in confusion and locked their gazes on him. Issei’s body was calm, but his eyes were worried. After all, the cry they heard was a distress call. Next to him, Yuutarou was tense, fins flared defensively, ear fins twitching in the water, eyes wide with…fear. “You two need to hide, ok? Hide, and block out the sounds like Papa taught you to.” Issei nodded and grabbed his younger brother’s arm in an attempt to get him to come and hide. But Yuutarou didn’t budge. He stared at Tooru.

“B-but, dad…what are you going to do?” he asked. His body trembled, but he stared at Tooru evenly. Tooru knew he wouldn’t move until he got an answer.

“I’m going to investigate,” he replied honestly.

“Then, I’m gonna,” Yuutarou began but Tooru stopped him with a look.

“You will go with your brother. Hide and don’t come out until I tell you it’s ok,” he ordered firmly. His son looked down, fins drooping, and Tooru felt a flash of guilt, but that disappeared as the cry was repeated. He bit his lip and looked around, trying to find anything that could be a trap. The humans had become increasingly cunning, but Tooru couldn’t see any indications of machines or humans in the immediate area. He looked back at his sons. “Go. Hide. I’ll be right back.” Issei nodded and dragged his younger brother along behind him.

Tooru knew he could rely on his oldest to keep the younger mer in check and stay hidden until it was safe to come out, so he turned around and started making his way toward the sound. The entire way, he kept his eyes peeled for anything out of the ordinary.

Nothing seemed to be abnormal, and that only made Tooru more anxious. If it was a mer in distress, an actual mer and not one of those fake ones the humans made, why wasn’t there more around? After the battle with the humans, so many decades ago, it was common practice for everyone to travel in groups of two or more. _So why aren’t their companions answering?_ Tooru wondered. And then, the thought struck him. _What if they’re all dead? What if this one is the only one left?_ A wave of nausea swept over him and he had to stop and calm himself before continuing forward.

Another cry drew his attention. He scanned the ocean floor beneath him, and his attention caught on a patch of seaweed. Something moved unnaturally there. It struggled against the flow of the water, against the weeds. Tooru crept closer, fins flared and body tensed, ready to turn and flee at a moment’s notice. His heartbeat wildly in his chest and he couldn’t stop the flashes of harpoons and the memory of pain that flooded his mind. _Why did I come alone? Why am I stupid?_ He could almost hear the thoughts in Hajime’s voice. _Hajime._ His mind latched onto his partner’s name. He’d promised not to communicate with him while he was on-duty unless it was an emergency. _Maybe this qualifies,_ Tooru reasoned as he thought of his sons, trembling and hiding, far behind him. Tooru kept his eyes on the unnatural-looking lump in the seaweed, but he stretched out his mind, feeling, searching, and there! There was Hajime.

_‘Hajime!’_ he called out telepathically. _‘Hajime!’_

_‘Tooru, what are you doing? I said for emergencies only! This is really distracting, and – ’_ Hajime began to scold him but Tooru didn’t let him finish.

_‘You need to come and get our sons! There’s something wrong. Something suspicious is here and I can’t see if it’s related to humans or not!’_ That was all he said. He felt Hajime trying to ask questions, but Tooru ignored them and instead sent him an image of where the area their sons were at. He didn’t wait for a response to that. He knew Hajime would never abandon their children. He trusted his partner completely.

Flexing his fingers, mostly in an attempt to get rid of the nerves, Tooru eyed the lump in the seaweed again. Another cry came from it, weaker this time. He inched toward the shape. It didn’t move. Tooru continued toward the lump and as he drew closer, it took on a more familiar image. A tail. A head. A back. Fins. And something…metallic-tasting in the water. _Blood,_ Tooru realized with a jolt. He continued forward, faster now.

“Hello?” he called to the mer in the seaweed. There was silence, and the body tensed and struggled some more. Tooru could see now, the mer was trapped in a net. It looked old, but strong. The material was digging into the mer’s skin and scraping their scales. As the mer shifted and turned, Tooru could see he was young. His hair was blonde, with two dark streaks that ran around his head. His eyes were tired and golden-brown. As Tooru approached, the eyes locked on him, and the mer tried to back away, but he didn’t move much. His skin clung to his bones and his cheeks were sunken. His tail twisted feebly in his constraints, the scales dull and dirty. Tooru softened his gaze. “Hey there,” he murmured. He reached out a hand, and the other mer didn’t seem to have the energy to pull back anymore. He just watched as Tooru’s hand came closer and closer, until he touched his cheek gently. “I’m not going to hurt you.”

_‘Tooru! Tooru! Answer me! I found Issei and Yuutarou! Where are you?! Dammit!’_

Tooru ignored Hajime’s voice, focusing on the mer in front of him. He didn’t want to scare him completely, but it was not clear if the young mer understood him. Tooru reached out with his mind. _‘Hello. Can you hear me?’_ Confusion flashed through the young mer’s eyes, and Tooru took that as a yes. He focused on sending feelings, rather than thoughts. _Safety. Safe. Safe. Safe. Help. Help. Help._ Tooru poured as much of his energy as he could into making sure the other mer understood he was only trying to help. Eventually, the mer’s eyelids fluttered closed, though Tooru was sure it was more from exhaustion than a sense of safety and trust. Either way, it didn’t matter.

He worked quickly, fingers gently plucking and pulling the netting off the young mer. He did his best to prevent it from giving him anymore cuts, and to keep the ones the younger mer already had from getting worse. Tooru was so absorbed in his work, he didn’t notice he wasn’t alone until he felt a hand on his shoulder. Tooru yelped and did his best not to jump. He turned his head to look over his shoulder and found himself face-to-face with a very grumpy Hajime. His fins were flared in aggression and his other arm was flexed at his side, ready to move, to grab, to defend, to attack.

“Ah. Hajime,” he greeted awkwardly. Movement behind his partner caught his attention and he saw Issei and Yuutarou craning their necks to see what was going on from a distance. No doubt Hajime had told them to stay back while he approached the scene. The kids always listened to him. Hajime’s eyes narrowed.

“Tooru. What the hell were you thinking, going off alone after something suspicious!” Hajime snapped. He leaned forward with a glare, baring his sharp teeth, and Tooru wanted to lean back a bit, but he stood his ground. The young mer was still wrapped in the netting, and one wrong move could make the material dig into his skin, or, even worse, Tooru could lose his grip on the netting and the shifting water would tangle it up and undo his hard work. And, he didn’t feel he was entirely in the wrong.

“I heard a suspicious noise. I just wanted to check it out,” he replied calmly. “When I got here, I found him.” He nodded his head to the now-unconscious young mer. Hajime’s eyes flicked downward, then they widened. His fins relaxed and he dropped back. His frown was one of confusion now.

“…he ok?” he muttered finally. Tooru bit his lip and surveyed the young mer caught in the net.

“I’m…not sure. He looks young. Too young to be out on his own. And I don’t know how long he was caught in this net,” he replied. Hajime grunted. Then he looked back up at Tooru.

“Need help? I’m not…good at the untangling and stuff…but I can hold things,” he offered. Tooru nodded.

“Ok, hold this bit here. I need to make sure it doesn’t get tangled back around him.” He handed Hajime one of the parts he’d been holding and worked on detangling more.

It took a while for them to get the net off the mer. Tooru was a little surprised he didn’t rouse while they worked, but then again, considering the state he found him in, the mer was probably undernourished and in pain. About halfway through the process, Issei and Yuutarou crept over to see what exactly their parents were doing. Which led to each of them being handed a handful of netting to hold to prevent it from becoming re-wrapped around the young mer.

Finally, the stranger was free. Hajime looked at Tooru. “Now what?” he asked. Tooru pursed his lips.

“Well, there was no one else around, so I think it’s safe to say he doesn’t have family…at least none nearby that we could bring him to. And I wouldn’t even know where to start looking, so I think for now we bring him back to the Pod, help him rest and heal, and go from there,” Tooru replied after a moment’s thought. Hajime nodded. He looked at the netting in his and their sons’ hands and frowned. Tooru pursed his lips. It would be bad to leave that here and risk another mer, or even other sea creatures, getting caught up in it. A shadow passed over them and the four of them looked up to see what looked to be a small boat passing over them. It looked like it would only fit a few people, and didn’t seem to be equipped with any of the gear humans usually used to hunt them.

“Just a second. I gotta get rid of this.” He gathered all of it up and then swam, up and up and up. He reached the surface, and Tooru winced. The transition to breathing air was always a painful one. He watched Hajime move as though throwing something, then he darted back down to them. “Let’s go,” he urged quickly, and he scooped up the unconscious stranger and started home, leading the rest of them. The boat did not follow them.

It was on the way home that Tooru decided to address what had been bothering him. He used his affinity, so he could talk directly to Hajime without their sons hearing what he had to say.

_‘I think you owe me an apology,’_ he started off. Hajime glanced at him, but didn’t speak out loud. He’d slowed the pace when he realized the boat didn’t have any intention of following them at all. Their sons now swam a few meters ahead of them, casting curious glances back every few minutes to the stranger in their Papa’s arms.

_‘For what?’_ Hajime asked finally. Tooru raised an eyebrow at him, then turned to face ahead.

_‘For how you acted when you found me,’_ he answered calmly, but he made sure Hajime could feel a shadow of how upset he was.

_‘Oh, what? I can’t even be worried about you?! Tooru, you told our kids to hide, and then went off to find potential danger ON YOUR OWN!’_ Hajime didn’t bother to filter out his feelings and Tooru winced as he felt the full extent of his partner’s fear and worry.

_‘That’s not it. Yeah, what I did was stupid and I should’ve asked you to come first and maybe bring some others along so we could investigate together, but you had no right to treat me the way you did.’_ Tooru heard the low growl Hajime gave off and he flicked his ear fins in warning. Hajime cut the sound off before either of their sons picked up on it. A fight was not something they wanted them to see right now, not when they were already stressed over what happened.

_‘So, what, you expect me not to be worried over my partner?! That’s…That’s…’_ Hajime couldn’t put it into words, but Tooru picked up on his distress.

_‘It’s not that! You have a right to be worried. The problem is how you acted. You need to stop responding to everything with aggression! We talked about this,’_ Tooru started upset, but he finished gently.

At that, Hajime paused, both mentally and physically. He was frowning, but looking down at the ocean floor. Then he closed his eyes and groaned. “Fuck. I was an ass, wasn’t I?” he muttered. Tooru bit his bottom lip.

“A bit, yeah,” he confirmed. Hajime sighed. He looked at Tooru.

“I’m…I’m sorry. I didn’t…I mean…How do…How can I make it better?” he asked, his eyes full of genuine contrition. Tooru gave him a soft smile. He could see their children speeding up ahead of them. They were picking up pace in the excitement of being so close to their den now.

“You can’t make what happened better. And neither can I. Let’s be honest, I didn’t exactly help the situation. Just…keep working on managing your temper, ok?” he offered. Hajime nodded. “And I will keep working on…uh…”

“…not being dumb?” Hajime suggested with a smirk. Tooru’s eyes widened.

“Hey!” He gave Hajime a glare, but it didn’t last long and then he was struggling to keep a grin off his own face. He whirled around, not wanting to give Hajime the satisfaction of seeing him smile. “Let’s go home.”


	2. Rough Waters

**Summary for the Chapter:**

> The new mer wakes up in a strange den. Things go downhill for Yuutarou from there.

**Notes for the Chapter:**

> Hello! Hope you guys are enjoying this AU and this fic! 
> 
> I want to warn you that there will be abuse, physical and verbal, addressed in this chapter, and there will be family arguments, fighting, and aggression. It is part of the storyline, but I still want you guys to be safe, so please be careful if that sort of thing triggers you.

The strange mer wasn’t very active. Yuutarou regarded him curiously, resting in their den now. It had taken some convincing to the pod leaders, and Yuutarou didn’t really pay attention to the conversation until the end, when it was decided the young mer would be staying temporarily with his family. He wasn’t sure how to take this news. He liked having his older brother around, and the idea of a new merperson was exciting. But he didn’t know anything about this mer and that made him nervous. Issei didn’t seem to be as conflicted about the whole thing. He just nodded and accepted the role as big brother to yet another mer. Yuutarou pursed his lips and flicked his fins. He would do it too. He would be as good as his older brother, and he would take care of this new younger brother, he decided.

It was as he decided this, that the strange mer stirred. Yuutarou snapped to attention and watched eagerly. The mer shifted and groaned and Yuutarou’s eyes widened.

“Papa! Dad!” he called out. “He’s moving!” His parents, who had been talking in hushed voices across the den, turned toward them. His Papa’s eyes widened and he shouted.

“Yuutarou! Back away,” he snapped. Yuutarou flinched backward. A snarl came from behind him, but before he could even turn around, he was grabbed and pinned down, sharp nails digging into his arms and sharp teeth snapping right next to his ear. A squeak of fear escaped him, much to his embarrassment. Yuutarou squirmed under the weight of the new mer, but it only caused him to growl and push Yuutarou down harder. Panic rushed through him and he struggled to turn his head to the side, eyes darting around frantically, silently begging for help. “Oi!” The shout grabbed Yuutarou’s attention and made the mer on his back freeze. His Papa was there, a glare on his face, his fins flared out in a spectacular display. Behind him, his Dad and Issei were both tensed, eyes locked on the new mer, ready to defend at a moment’s notice. “Let. Him. Go.” His Papa’s voice was strong and unwavering. There was a moment’s pause, and then the new mer released him. Yuutarou shot up immediately and raced to take cover behind his Papa. Issei wrapped an arm around him and pulled him back a bit more. Trembling, Yuutarou turned to watch his parents confront the new mer. Part of him hoped they would say that it was impossible for him to stay there now, that he wouldn’t be a fit for their family. He was too scared to consider any alternative.

The stranger’s golden-brown eyes flashed and he snarled at their parents. Yuutarou squished himself closer to Issei and his older brother rubbed his shoulder soothingly, eyes locked on the scene in front of them. Their Papa approached the mer, who hissed and growled at him. He stopped for a moment, and then… _lowered his fins?!_ Yuutarou opened his mouth to protest, terrified of what would become of his Papa, but Issei slapped a hand over his mouth before he could make any noise. He could only watch in terror as their Dad approached as well, slowly.

“Hey there,” their Dad’s voice was gentle. Yuutarou felt his fins bristle a bit. _Why would he be so kind to someone who attacked me?_ He wondered. “It’s ok.” _No, it’s not!_ Yuutarou wanted to protest, but if he so much as twitched, Issei would just hold him tighter. He was squished against his older brother’s chest, and he could hear his heart racing. Yuutarou swallowed and closed his eyes.

_‘Papa? What are you doing?’_ he asked hesitantly. He wasn’t the best at telepathy, but he could manage a direct conversation. He got no response. _‘Papa?’_

_‘Quiet, Yuutarou.’_ His Papa’s inner voice scolded him. Yuutarou flinched and withdrew even more against his brother, eyes wide open now and locked on their parents.

They watched as their parents continued to approach slowly, speaking quietly.

“It’s ok.” It was their Papa speaking now. “I know, Yuutarou must have startled you by being so loud.” Yuutarou frowned.

_‘I didn’t!’_ He started to protest, but his Dad cut him off.

_‘Shh, Yuutarou. Not now.’_

Yuutarou gripped his brother’s fins and felt a pain settle in his gut. Next to him, Issei hissed softly in pain. Wide-eyed, Yuutarou immediately let go of his brother’s fins. He was about to ask if he was ok, but Issei just gave him a pained smile and patted his shoulder.

“You’re safe here. None of us will attack you. But we won’t let you just attack others, either,” their Papa continued in a firm voice. The mer regarded them all with narrowed eyes, his tail flicking back and forth behind him. “I promise you, I am more than capable of taking you down if needed. I’m going to back off completely now, ok? Then you can relax.” He relaxed his fins.

“Hajime!” Their Dad protested.

“It’s fine, Tooru. He knows who is in charge here.” Yuutarou tensed as he watched his Papa and Dad withdraw from the mer. The mer watched them with suspicion for a moment, then curiosity. After a moment, his posture relaxed slightly and he crept forward. Yuutarou could almost hear the smile in his Papa’s voice as he spoke again, “See? He’s doing just fine. We’ll take it slow.” The mer was right in front of their parents now, and he tilted his head, watching them, as if still uncertain exactly how much he could trust them. “What’s your name?”

The stranger mer blinked at the question directed at him. He furrowed his brow and seemed to be thinking for a few moments. His mouth opened and closed. His throat moved, and garbled noises came out. Yuutarou wondered if he even knew how to talk. As if on cue, the mer muttered a name. “Kentarou.”

“Hello, Kentarou,” their Dad greeted. Kentarou glanced between the two older mer. “I’m Tooru. This is Hajime, and our sons: Issei and Yuutarou.” He gestured to each of them and Kentarou let his gaze slide over each of them. His eyes narrowed as he looked over Yuutarou, but he said nothing. “We found you tangled in that netting.” At the mention of how they found him, Kentarou tensed and his fins flared up slightly. “We couldn’t find anyone else around, so we brought you home to our den and Pod. You’re welcome to stay with us until we can get you back to your family.”

Kentarou relaxed again, but his face remained twisted in a frown. “Don’t have any,” he mumbled.

“I’m sorry, I didn’t quite catch that,” their Dad replied. Kentarou’s mouth twitched, but he answered again.

“I don’t have any family.” His voice was louder now. Yuutarou thought it sounded gruff and angry. Their parents exchanged a look, and Yuutaoru knew they were having a discussion none of the rest of them could hear. Finally, they turned back to Kentarou.

“In that case, you are welcome to stay with as long as you like,” their Papa replied. “There will be rules you have to follow, but it’s better than being out there on your own. We can try to look at other solutions as well if you’d like.” Kentarou narrowed his eyes, as if somehow this was a trap. _It is a trap. A trap for me,_ Yuutarou thought bitterly. After a moment, the new mer nodded.

“Ok.”

***

Yuutarou examined the empty shell in his hands. It was an old crab shell, abandoned now that the crab was too big for it. It was smooth and he liked the colour. He hummed softly to himself as he ran his fingers over the edges. A shadow fell over him and he sighed. He knew who it was without even turning around. It had been three weeks since Kentarou joined their household, and Yuutarou hadn’t been able to go anywhere without the other mer tagging along. It grated on his nerves. Especially as Issei didn’t seem to have to deal with the same issue. In fact, he hardly saw Issei around at all. His brother kept going off to play with his friends at their dens.

“What are you doing?” the gruff voice pulled Yuutarou out of his reflections. He sighed and dropped the shell.

“Nothing,” he muttered. He glanced over his other shoulder, noting his Dad chatting idly with another pod member. He sighed again and turned back around, pointedly avoiding Kentarou. He swam forward slowly, lazily, trailing his hands in the sand. He hummed and flipped onto his back…only to see Kentarou hovering right over top of him, frowning at him. Yuutarou yelped in surprise and scrambled so that he was upright. “What are you doing?!” he demanded. Kentarou tilted his head and looked him up and down, as if _he_ were the one acting oddly.

“Watching you,” was the simple answer. Yuutarou glared.

“Well stop it! It’s creepy,” he snapped. “Just leave me alone!” Kentarou’s fins flared slightly as Yuutarou’s volume rose.

“I do what I want!” Kentarou growled back. Yuutarou could feel his own fins rising in annoyance and he clenched his fists.

“I don’t care! I don’t want you around me! Back _off_!” he shouted. He spun around to leave, only to have his arm grabbed. Kentarou yanked him back around, snarling. Yuutarou couldn’t help the yelp that escaped him, and he stared at Kentarou’s angry face with wide eyes.

A gentle hand came to rest on both Kentarou’s and his arms. They turned their attention from each other to the owner of the hands. Yuutarou felt relief rush through him at the sight of his Dad, but only for a moment. His Dad was turned toward Kentarou, with a gentle expression on his face. “Hey, Kentarou. You can let him go. It’s ok.” It took a few more moments of conversation, mostly just his Dad repeating those words, but Kentarou finally let him go. Yuutarou snatched his arm back and glared at the other mer as he rubbed his arm. His Dad turned to him. “Yuutarou,” he chided, “you know Kentarou startles easily at loud noises. You shouldn’t yell at him.”

“But!” Yuutarou started to protest, but his Dad cut him off.

“No ‘buts’. You don’t need to yell. You two can talk nicely to each other,” he interrupted with a stern look directed at both of them. Kentarou looked down at the ocean floor, fins drooping slightly. Yuutarou bit the inside of his cheek and glared downward as well. He clenched and unclenched his fists at his sides, his fins bristling and his tail flicking back and forth. “Something you want to say, Yuutarou?” Yuutarou shook his head and continued to glare at the sand beneath him. “Are you sure? You look like you want to say something,” his Dad prompted. Yuutarou pursed his lips and shook his head again. “Yuutarou.” His voice held a warning tone now. Yuutarou glanced up to find both mer staring at him, Kentarou with a stony expression, his Dad with an expectant one.

Looking away, he muttered, “I don’t want to always have him around me. He always follows me and it’s annoying.” He heard his father sigh.

“Yuutarou, that’s not a nice thing to say,” he scolded gently. Yuutarou felt his whole body tense up and he couldn’t stop himself from snapping back.

“Yeah, well, it’s the truth! I don’t care if it’s nice or not!” He didn’t look up at either of them. Instead, he spun around and darted off.

“Yuutarou! Stop!” He could hear his father calling to him, but he ignored him and sped up. He could hear someone barreling through the water behind him and he tried to stay ahead of them.

A hand gripped his tail and yanked backward. Yuutarou yelped as he was effectively dragged back. He twisted his body to look at his captor, and sure enough it was Kentarou. “Let go!” he hollered, but Kentarou only growled and pulled harder.

“Stop! Kentarou, let go of his tail. Yuutarou, you stay right here and listen to me,” Tooru’s voice rang with authority, the kind that Yuutarou wouldn’t dare to defy. He stopped struggling and Kentarou released his tail. Yuutarou turned slowly to fully face his parent. The look on his face was a mixture of annoyance and disappointment, which made Yuutarou cringe and look down. The sigh that left his Dad’s mouth sounded exhausted. “Kentarou, you can’t just grab someone else’s tail.” There was a pause.

“Sorry,” came the gruff reply. Yuutarou didn’t acknowledge it.

“And, Yuutarou.” His Dad’s voice was definitely sharper now. “You know better than to try and swim off on your own. You aren’t old enough to go off alone! What if humans caught you? What if you were attacked by some other sea creature?! You’re still learning how to defend yourself, you aren’t ready for that!” Silence descended and his words sank into Yuutarou’s mind like a rock in water. He couldn’t keep his limbs from trembling and his chest felt tight. A lump formed in his throat and he forced himself to swallow past it, even as his lips wobbled. “Do you understand?” It was a simple question, but Yuutarou couldn’t find it in himself to form the words, so he nodded silently. “You’re going back to the den. Both of you. Let’s go.” Neither of them argued. They fell into line and followed Tooru back to the den. Yuutarou focused his gaze entirely on his Dad’s fins in front of him. He didn’t look away once. So he didn’t see Kentarou pause and scoop something up from the ocean floor before hurrying to catch up to them.

***

Issei was prepared for Yuutarou’s moping. He was ready for his little brother to vent and blow off steam, like he did every other day. He was totally ready with stories about what Takahiro and he did earlier that day to cheer him up, and he expected Yuutarou to be settled in a corner of the den, refusing to make eye contact with anyone until he poked him enough times to make him laugh before they even got to talking. He was not ready to come home to tense silence and Yuutarou curled up on his side, not even tracing his fingers along the rock of their den. Issei blinked and surveyed the scene. Yuutarou was on his side, unmoving. Kentarou was across the den, curled up, but staring…or maybe glaring?...at Yuutarou. Tooru was busy descaling fish for their dinner, but his face and shoulders were tense. Issei didn’t like seeing him like that, but he figured it wouldn’t help for him to bug his Dad right now. He didn’t know how to really interact with Kentarou, and that left Yuutarou as the only option.

Quietly, Issei drifted into the den. He nodded a greeting to his Dad, who only looked up once before turning back to his work. He could feel Kentarou’s eyes on him, so he offered a wave which the other mer returned. Issei settled on the den floor next to his younger brother. He nudged him, but Yuutarou didn’t respond. He frowned and poked his younger brother in the shoulder. “Hey.” Yuutarou didn’t even flinch. Issei poked him again. And again. And again. He kept poking until he saw his little brother’s tail flick in annoyance. He smirked. And poked him again, this time much harder than before. Yuutarou flipped over and shoved at him. Issei laughed as he rocked back slightly. “Got your attention, huh?” A scowl was the only answer he received. “Awww, come on, what’s eating at you?” Yuutarou flipped his tail in the water, his fins twitched and Issei saw his eyes dart between their Dad and Kentarou, before he finally fixed his gaze on the floor. Issei pursed his lips. He was just about to start a telepathic connection, but Yuutarou beat him to it.

_‘I don’t wanna talk about it.’_ His tone was dull, and Issei could feel a tinge of shame colouring his thoughts.

_‘Come on, tell me what’s bothering you. I’m your older brother.’_ Issei prodded at his younger brother’s arm again. Yuutarou glared at him and shifted away.

_‘Stop it. I don’t want to talk.’_ He rolled over and faced the wall again. Issei raised his eyebrows. He couldn’t help but sneak a glance at his Dad and Kentarou. Tooru was still busy preparing their food. Kentarou was watching their exchange curiously. Irritation coursed through him. He knew whatever happened involved the newest member of their household; it had been like that since he got here. Anytime Yuutarou was sulking, it seemed Kentarou was at the root of the problem.

_‘What did Kentarou do?’_ Issei demanded. Yuutarou stiffened. Then he relaxed.

_‘How did you know?’_

 _‘Lucky guess. Tell me what happened.’_ There was a long pause, and Issei was about to repeat his question when Yuutarou finally replied.

_‘He just…he keeps following me everywhere. And I hate it. But he won’t leave me alone. So I tried to leave, just to get away for a while, and Dad told me to stop but I didn’t listen, and then…then Kentarou was chasing me and he grabbed my tail and – and it HURT. And then everything was MY fault.’_

Issei had to clench his fists as he felt the overwhelming shame and pain pour out of Yuutarou. He grit his teeth and did his best to keep his fins from flaring up. He hated his brother being in pain.

A movement at the entrance to their den drew his attention and Issei looked up to see his Papa enter the den. Yuutarou glanced over his shoulder before turning his attention back to the wall, shoulders tense and tail flicking irritably in the water.

“I’m home,” Hajime announced. Issei nodded at him. Tooru looked up.

“Hajime,” he greeted with a tired expression. Issei watched his Papa stop and raise an eyebrow, surveying the inside of their home.

“…what happened today?” he asked resignedly. Their Dad sighed before responding.

“Yuutarou thought it would be a good idea to swim off on his own. Kentarou helped me stop him,” he answered. Yuutarou flipped back onto his other side, facing their parents with a glare.

“He didn’t ‘help you stop me’! He yanked on my tail!” he shouted in protest. Issei flinched. _Not good,_ was the only thought that went through his mind before their Papa snapped.

“You thought it would be a good idea to just go off on your _own_?! _What_ in the hell were you thinking? _Were_ you even thinking?! Do you know how _dangerous_ that is??!” He snarled as he approached them. Yuutarou’s eyes widened and he scooted back, his back pressed up firmly against the wall of their den. Issei swallowed thickly. His heart raced in his chest and his fins trembled slightly.

“I…I-I d-didn’t…” Yuutarou stammered, but their Papa didn’t let him finish.

“Of course, you didn’t think! You _never_ do, do you?!”

Yuutarou’s jaw snapped shut and he glanced around, looking for an escape. Issei felt his limbs lock in place.

“Pl-please,” Yuutarou started, but he was interrupted again.

“Shut _UP_! You shut up! You don’t get to talk. You could’ve put yourself in danger! You could’ve put Tooru or Kentarou in danger!”

“Hajime,” their Dad tried to cut in, but Hajime didn’t listen. He kept advancing, towering over the two young mer. Issei glanced at his younger brother. He saw his wide eyes, his pale face, tremors running through his body, his teeth digging into his bottom lip. Yuutarou was the image of sheer terror. That was what pushed him to act. Issei shifted so he was in front of Yuutarou. He shoved himself into an upright position. Hajime stopped and glared at Issei. Issei clenched his fists and tried to slow his breathing. He flared his fins, effectively blocking his younger brother from view.

“St-stop yelling at him,” he choked out. He felt like he couldn’t breathe. Behind him, he heard shuffling and a quick glance back told him Yuutarou was moving closer to him.

“Hajime!” Their Dad called again. He was right behind Hajime now, and he put a hand on his shoulder. “Hajime, I already went over it with him. I was just letting you know what happened.” Hajime jerked away from him. “Hajime, STOP!”

“I’m so-so-sor-ry!! I’m sorry! Pl-please!” The sudden outburst came from behind him and Issei tensed even more.

“Stop your bawling, or I’ll give you something to cry about! Issei! Move!”

Issei felt the blood rushing through his body, heard his brother struggle to contain his sobs, but all he saw was his Papa’s angry face. Angry, aggressive, fierce, strong. He had his arm raised and Issei flinched and turned his face away. There was a shout and he saw his Dad reach to grab Hajime’s arm from the corner of his eye. He felt the water move and closed his eyes, braced for the first blow…but it never came. After a moment of listening to his brother’s hiccups and sobs, Issei opened his eyes. The sight that met him startled him. In front of him, hand on his Papa’s arm, was Kentarou. His fins were flared and, Issei couldn’t see very well due to the angle, but it looked as though his teeth were bared. A low growl rumbled out of his chest. Hajime blinked. He held Kentarou’s gaze for a moment. Then he relaxed his arm and shoulders.

The instant their Papa relaxed, Kentarou released him. He swallowed and surveyed the three younger mer in front of him…or rather, the ones he could see. Yuutarou was still effectively blocked by Issei’s fins. Hajime’s jaw twitched and he looked away. “…I…I need to go,” he muttered. Then he spun around and left the den. Issei remained in front of Yuutarou, watching Tooru now. He stared after his mate, before turning back and facing his sons. Issei held his Dad’s gaze evenly for a few moments. Eventually, Tooru turned around and went back to preparing dinner, without a word to any of them. But Issei saw his hands were shaking. He ignored his father and turned around. Yuutarou was curled up behind him, trembling, eyes on the ground.

Issei relaxed his fins and slowly lowered himself to the ground. He reached out hesitantly. “Hey. Yuutarou,” he murmured. Yuutarou looked up at him, his eyes large and still full of fear. “He’s gone away for a little while. I’m sure when he comes back, he won’t still be mad.” Yuutarou bit his lip and nodded, eyes back on the ground. Issei let his hand come to rest on his brother’s shoulder. Yuutarou flinched slightly at first, but then he relaxed.

“I…don’t understand,” Kentarou stated. Issei looked up to see the mer hadn’t moved from where he’d come between them and their Papa. “Why was he going to hit?” Their Dad tensed, but he didn’t answer, just kept working.

“…because he was angry,” Yuutarou whispered finally. “Because I was bad.” He turned his gaze upward abruptly, his stare accusing. “You would’ve too! Don’t pre-pretend like you’re any different. You get plenty aggressive, too!” Kentarou glared back at him.

“I am not!”

“You yanked on my tail!”

“Hey, guys,” Issei tried to interject, but neither appeared to have heard him. He could see their Dad had stopped moving and was glaring at the fish in his hands. _Not good._

“That was different!”

“How was it any different? It’s the exact same!”

“No, I only did it because you weren’t listening to Tooru!” Kentarou protested.

“Yeah, and why do you think Papa did what he did just now?!” Yuutarou countered. He crossed his arms and stared defiantly up at Kentarou.

“You two,” Issei heard their Dad’s voice, and his warning tone. But the other two carried on.

“It doesn’t make sense! You were already in the den when he got here! You weren’t trying to swim off alone!” Kentarou leaned forward as he spoke, effectively towering over Yuutarou. Yuutarou continued to glare up at him and flared his fins slightly.

“Shut up! Don’t pretend…you’re…you…You are just as bad as he is, and that’s all there is to it!” Yuutarou’s chest was heaving and his gills flared open. Issei tried to separate them physically, but neither of them would budge. “What doesn’t make sense is you helping us! Don’t pretend you didn’t – didn’t _want_ to see me in trouble, see me get punished!”

Kentarou growled. “I didn’t want to see you hurt! I grabbed your tail to _protect_ you! It’s dangerous on your own! _He_ was going to _hurt_ you!”

“No one was going to hurt _anyone_!” Their Dad cut in sharply. “That’s enough!”

“I didn’t ask you to protect me!” Yuutarou snapped, ignoring their father completely. He lunged forward, and Issei had to use a good amount of strength to hold him back.

“Guys, stop,” he began. Yuutarou struggled in his arms, too intent on lunging at Kentarou to pay attention to anything anyone else said.

“You don’t need to ask! It’s common sense! The weakest ones need protection, or they’ll _die_!” Kentarou shouted, his fins fully flared and his golden-brown eyes wide with aggression. Yuutarou’s eyes widened and Issei cursed internally. He barely managed to tighten his hold before his younger brother lunged again.

“I AM NOT WEAK!” he screamed, hands reaching, nails scrabbling, tail thrashing, eyes wild. Kentarou snarled, and then Yuutarou was ripped from Issei’s arms. Issei yelped and watched with wide eyes as Kentarou wrestled and pinned him to the floor of the den.

“You. Are. Weak. I am strong.” The words were growled so low Issei barely heard them. Yuutarou thrashed and struggled underneath Kentarou, to no avail. Issei couldn’t move, frozen in shock, and neither, it seemed, could their father. After several minutes, Yuutaoru finally went still, too tired to fight anymore. That was when their Dad apparently regained his voice.

“Kentarou. Let Yuutarou go. You shouldn’t pin him to the ground like that. And stop calling him weak. It isn’t nice,” he stated as calmly as he could, but Issei could hear the nervous undertone to his voice. Kentarou waited an extra moment before releasing Yuutarou. Issei watched his younger brother scramble away from all of them, retreating into the corner furthest from them, facing outward, as if he was watching for potential threats. The thought made a pang shoot through his chest. Issei turned away with a grim look on his face.

He had not been prepared for this at all.

**Notes for the Chapter:**

> Some notes:
> 
> Hajime is struggling with mental health, and so is Tooru, because of the previous large fight the mer had with humans, and subsequent interactions with humans that have been just as harsh. Anxiety and depression tend to present more as anger in males, largely influenced by the fact that society expects men to be strong and discourages them from expressing emotions that may make them seem weak. What things can set them off and what things they will be ok with can be unpredictable. They both need to work on that, because it's starting to interfere with their parenting.
> 
> Kentarou has also been traumatized, though that has not quite been addressed yet, but he has also been taught that he needs to be strong and take care of the weak. His first interaction with Yuutarou, he was stronger than Yuutarou. This largely fuels his interactions with Yuutarou, who is trying to be independent.
> 
> Anyway, I hope you guys enjoyed it. Stay safe!

**Author's Note:**

> Hope you liked this! Thanks for reading :)
> 
> If you feel like it, some shout at me on tumblr, @m34gs
> 
> Stay safe!


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